Advice on replacement chain and cassette and other bit ?

[skyhawk]

Please see images

I guess my sons bike needs a new cassette, do you agree, and chain.

How will I know I am being sold a decent(ish) one and not a cheap one marked up, if it was my car I am well up on not being conned and knowing about cars, NOT bikes.

His is a Saracen Mantra, not expensive but looked after

Also image 2, why does the chain keep hitting the metal, despite Halfords (yes I know) fixing it

Thank you

[Jamesh]

Hi

A subrace SRAM or Shimano one will be ok about £10 upwards for one.

The front mech should be lower that it is so that the chain isn't rubbing on the bottom of the mech if it is the chain shouldn't rub the mech apart from cross it from small to small or big big.

Cheers James

[Norman H]

You should be able to get a decent 8 speed chain for around £10. If the new chain skips on the old cassette then you need to replace the cassette and possibly the chain rings. Otherwise you should be OK with the old cassette.

The old transmission looks as though it hasn't seen any lubricant in a while. I'm reluctant to restart the debate on the best way to maintain your transmission but if you search the forum for chain cleaning you'll find no shortage of advice.

[Brucey]

the sprockets are superficially rusty through neglect. They don't look worn out to me, but they might soon be if the bike starts to see a lot of use. If you don't know what you are looking at, my advice is not to buy the cheapest chain; buy a mid-price one instead; most chain manufacturers produce a cheap chain that doesn't last long, but in the mid-range they are much of a muchness.

The chain is hitting the front mech because

a) it isn't adjusted correctly
b) the gear in use is running too far 'cross chained'
c) the FD need 'trimming'

Re b) you shouldn't expect to use all the gears at the back with every chainring; if the chain runs at an extreme angle it causes all kinds of problems. Sometimes the FD won't shift onto the small chainring unless it is set as yours is, i.e. it will then rub in some of the other gears. With relatively inexpensive parts this isn't uncommon. It thus isn't uncommon to have to 'trim' the FD to avoid rubbing in some gears either. However not all shifters allow trimming either.

FWIW I have had good luck when using KMC chains when the chain is reluctant to shift onto the small chainring, but on some bikes 'perfection' simply cannot be attained; the parts are mismatched, dysfunctional or worn enough that they'll never work in an ideal fashion.

cheers